= Uses-allocator Construction To support code bases which are already using polymorphic allocators, the containers in this library support {std_uses_allocator} construction. For <<ref_array>>, <<ref_object>>, <<ref_string>>, and <<ref_value>>: The nested type `allocator_type` is an alias for a {ref_polymorphic_allocator}. All eligible constructors which accept <<ref_storage_ptr>> will also accept an instance of {ref_polymorphic_allocator} in the same argument position. The member function `get_allocator` returns an instance of {ref_polymorphic_allocator} constructed from the {ref_memory_resource} used by the container. Ownership of this memory resource is not transferred. Practically, this means that when a library container type is used in a standard container that uses a polymorphic allocator, the allocator will propagate to the JSON type. For example: Library containers can be constructed from polymorphic allocators: The polymorphic allocator is propagated recursively. Child elements of child elements will use the same memory resource as the parent.